This invention relates to the noninvasive measurement of blood pressure, and more particularly to the noninvasive measurement of blood pressure by the oscillometric method.
A number of noninvasive methods of measuring blood parameters are known. For example, blood pressure has been measured by the auscultatory method which uses a cuff and a stethoscope, and by the oscillometric method which only requires a cuff applied to a body member. The conventional oscillometric method relies on the small-amplitude pulsatile pressure oscillations communicated to the cuff by the underlying artery in the body member during cuff deflation from above systolic pressure to zero pressure. Such arterial pressure oscillations cause corresponding small oscillations in cuff pressure which can be amplified and used to identify systolic, mean and diastolic pressure. For example, it has been established by Posey et al. that the cuff pressure for maximal amplitude oscillations corresponds to mean arterial pressure. See Posey et al., “The Meaning of the Point of Maximum Oscillations in Cuff Pressure in the Direct Measurement of Blood Pressure,” Part 1, Cardiovascular Res. Ctr. Bull. 8(1):15–25, 1969. See also Ramsey, “Noninvasive Automatic Determination of Mean Arterial Pressure,” Med. Biol. Eng. Comput. 17:17–18, 1979; and Geddes et al., “Characterization of the Oscillometric Method for Measuring Indirect Blood Pressure,” Annals of Biomedical Engineering, Vol. 10, pp. 271–280, 1982. All such references are incorporated herein by reference.
Commercially available oscillometric devices are useful for noninvasive blood pressure measurement, but a need remains for improvement in accuracy, particularly with respect to identification of systolic and diastolic pressure.